power: qpnp-fg-gen3: add support for skew in capacity learning algorithm

In some cases, a skew needs to be applied on the learnt capacity
to counter the error. Add support for it.

Change-Id: I7f80088e7db4e3414d86983722c92e4fc14323e0
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>